Make a person-to-person communication with your users. Marketing automation also helps with this.

Retention stage

In summary, stay in touch. Do this by both publishing content on your website relevant to existing users and sending them emails to draw their attention to this content.

In conclusion,

There are many ways of engaging users, but the important point of this blog post is communication with your leads does not stop once they buy. It transitions into a new phase where you treat them as a customer rather than a lead.